Incidence of<i>Ichthyophonus hoferi</i>in Puget Sound Fishes and Its Increase with Age of Pacific Herring

Abstract

A recent decrease in the mean age of adult Pacific herring Clupea pallasi in Puget Sound was associated with a high prevalence of Ichthyophonus hoferi, a protistan parasite that can be highly pathogenic to Pacific herring. In Puget Sound, high intensities of I. hoferi infection may be maintained in older cohorts of Pacific herring because the prevalence of I. hoferi increased with age from 12% among juveniles to 58% among the oldest, age-6 and older cohorts. Low intensities of I. hoferi infection in the region may be maintained in alternative fish hosts, such as surf smelt Hypomesus pretiosus, Puget Sound rockfish Sebastes emphaeus, Pacific tomcod Microgadus proximus, and speckled sanddab Cithanichthys stigmaeus.